Export face groups as paths(vectors)
There is a addon which does this. It works on both meshes and curves, and has many options for coloring and shading.

Here's a setup which will output flat shaded faces with the diffuse color of your materials (click for larger image):




In cycles the viewport color is actually the diffuse color, which is used by the addon.
For flat shading be sure to turn off most of the effects and variations, as shown in the screenshot
Once everything is set, click export to export the viewport as a SVG.


The result is shown in inkscape on the left.